Such methods and receivers are used, for example, in automotive technology in order to receive, with the minimum possible complexity and cost, radio applications in the vehicle having different transmission parameters.
For example, radio applications such as a “keyless or contactless remote-control entry system”, usually referred to as RKE (remote keyless entry), and tire-pressure monitoring, usually referred to as Tire Guard, are implemented in the vehicle with different transmission parameters because of different physical conditions and requirements (different range, information content, etc.).
In this case, the differences in the transmission parameters mostly lie in the data rates used and/or the modulation techniques used (amplitude, frequency, phase modulation ASK/FSK/PSK) for transmitting signals.
In principle, the signals from the different radio applications can obviously differ in any transmission parameters such as data rate, modulation type, wake-up criterion, synchronization and threshold value etc.
Solutions known in vehicular technology try to receive and determine a transmission parameter in which the applications differ, and, on successful determination, to switch the receiver into the relevant mode for further receiving.
Disadvantageously, the receiver for determining the transmission parameter is not optimally configured for at least one of the two applications, which introduces performance compromises. For example, if, for different data rates, the data-filter bandwidth is selected to suit the higher data rate, then the receiver is not optimally configured for receiving lower data-rate signals, and corresponding performance losses must be reckoned with.
Furthermore, this method is also highly application specific, which is why a microcontroller is needed to determine the transmission parameter and to then switch over the receiver into the relevant mode. This, however, has the disadvantage of causing an unwanted rise in the quiescent current.
In addition, patent DE 101 07 130 A1 discloses a super-regenerative receiver that requires no application-matched input circuit and that can demodulate the ASK and FSK signals. This receiver has a complex circuit design, however, and has an increased quiescent current consumption because of its quench-controlled sweep circuit.